Wrapper class variable in switch

[Vijay Chandran]

public class SwitchTest
{
    public static void main(String[] args)
    {
        Integer i = new Integer(1) + new Integer(2);
        switch (i)
        {
            case 3:
                System.out.println("three");
                break;
            default:
                System.out.println("other");
                break;
        }
    }
}

Dear friends,

We can pass primitive values like int,char to switch statement. But this code passes an object of Integer (wrapper) variable to the switch statement. The compiler didn't complain anything about this. It executed perfectly.

Please explain me why this happened.

Thanks in advance.
Regards,
Vijay

[Pho Tek]

autoboxing

[marc weber]

JLS - 14.11 The switch Statement...

SwitchStatement:
switch ( Expression ) SwitchBlock

...

The type of the Expression must be char, byte, short, int, Character, Byte, Short, Integer, or an enum type...

[Nicholas Jordan]

boolean testIfFound(Integer i)
{
boolean found;
final int switchValue = i.intValue();
switch(i)
{
case 0: found = true;
case 1: found = true;
// ..... and so on
// ..... and so on
// ..... and so on
// ..... and so on
// ..... and so on
// ..... and so on
}

return found:
}

[Rob Spoor]

Originally posted by Nicholas Jordan:
boolean testIfFound(Integer i)
{
boolean found;
final int switchValue = i.intValue();
switch(i)
{
case 0: found = true;
case 1: found = true;
// ..... and so on
// ..... and so on
// ..... and so on
// ..... and so on
// ..... and so on
// ..... and so on
}

return found:
}

You forgot the break statements.

[Vijay Chandran]

Thanks a lot for the reply.

Sorry for the delayed thanks!! Just now checked the forum.


Regards,
Vijay

[Nicholas Jordan]

[Rob Prime:]   You forgot the break statements.

Yes, I did - but the switch I wrote will cascade along the steppes and could have as well have been written:

Integer i = new Integer(1+2);
int switchVal = i.intValue();
boolean BooLean = (switchVal == 3 );
switch(switchVal)
{
   case 3 : System.out.println(Boolean.toString(Boolean.booleanValue(BooLean)));
}
if(!BooLean)System.out.println("Please explain me why this happened.");

Switch cases do not necessarily need the breaks, in this one the cascading down the chain just wastes a few dozen processor cycles ~ the effect is the same.
[ September 21, 2007: Message edited by: Nicholas Jordan ]